Ukrainian lawmakers have passed a bill to take back control of the country’s eastern territories from Russia-backed forces.

The bill, which was ratified Thursday, described Russia as an “aggressor country” and claimed that the Donetsk and Lugansk regions had been “temporarily occupied” by Russia.

The bill reiterated that Kiev needed to do its best to “re-integrate” those regions even if it was a matter of using military force.

The armed conflict erupted in Ukraine following the overthrow of pro-Russian president Viktor Yanukovych in February 2014 and intensified after people in the Black Sea peninsula of Crimea voted for reunification with the Russian Federation in a referendum in March 2014. The West brands the reunification as annexation of the territory by Russia.

The pro-Russians have turned the two regions of Donetsk and Lugansk in the east — collectively known as the Donbass — into self-proclaimed republics.

Armed confrontation between the pro-Russia forces and the Ukrainian military has killed more than 10,000 people, according to the United Nations.

A peace agreement was reached between the warring sides in the Belarusian capital Minsk in February 2015 under the supervision of Russia, Germany, and France to end the conflict.

Russian lawmakers swiftly reacted to the ratification of the new bill in Ukraine, saying it was a threat to the existence and function of the Minsk deal and other agreements reached before and after that in the Belarusian capital.

“Kiev has gone from sabotaging the Minsk agreements to burying them,” said Konstantin Kosachev, who serves as the head of foreign affairs committee in the Russian parliament’s upper house.

There was no mention of the deal in the bill passed by Ukrainian lawmakers.

Sporadic clashes have continued in eastern Ukraine despite the 2015 peace deal and other truce deals. The West keeps accusing Russia of feeding the insurgency. Russia denies any involvement in the conflict.